Or: which actually gets you the score
At C1+, TOEFL prep isn’t about learning English anymore; it’s about learning the test. That distinction changes the group-vs-one-on-one question, because what you’re optimising for is targeted correction, not general exposure.
Group classes are cheaper and give you something one-on-one can’t: other accents, other mistakes to learn from, the mild social pressure of a shared deadline. That’s genuinely useful for the Listening section, where you need exposure to a range of speakers. The cost is speaking time: split six ways, your actual airtime in an hour class might be eight minutes, and TOEFL Speaking is exactly the section where eight minutes a week won’t move your score.
One-on-one flips that trade entirely. Every minute is diagnostic, a tutor watching for your specific recurring errors, not generic ones. For a C1+ student the plateau is rarely vocabulary; it’s usually something narrower, a tendency to over-hedge in Speaking, weak transitions in the integrated Writing task, timing that falls apart under pressure. That’s the kind of thing a group class structurally can’t fix, because the lesson has to serve the average student in the room, not you specifically.
If you’re going to spend money on tutoring at C1+, spend it where the return is highest: get a proper diagnostic from a one-on-one session or two, find out exactly what’s actually capping your score, then decide whether the rest of your prep needs more one-on-one correction or just more timed practice, which you can do alone. Group classes are a reasonable way to keep exposure up in between; they’re just not where the score-moving work happens.
A few things that trip up C1+ students regardless of format: not practising under real time pressure (the test doesn’t care that you know the answer if you run out of time to give it), undertyped or fumbled navigation because the interface itself is unfamiliar, and over-polishing Speaking and Writing answers for complexity when the marking actually rewards clarity. A clean, simple answer delivered on time beats an ambitious one that runs out of road.